In the processing and packaging of semiconductor devices, wire bonding continues to be the primary method of providing electrical interconnection between two locations within a package (e.g., between a die pad of a semiconductor die and a lead of a leadframe). More specifically, using a wire bonder (also known as a wire bonding machine) wire loops are formed between respective locations to be electrically interconnected.
An exemplary conventional wire bonding machine includes an indexing system for moving a workpiece (e.g., a semiconductor die/dice on a leadframe) between a supply location (e.g., a magazine handler) and a bonding location using grippers or the like. Exemplary indexing systems include rails or the like along which the workpiece is moved during indexing. When the workpiece reaches the bonding location a support surface such as a heat block is raised to meet the lower side of the workpiece. A device clamp (also known as a clamp insert or a window clamp) is lowered to secure the workpiece from above. The device clamp defines an aperture(s) through which a wire bonding operation is completed. FIG. 1A illustrates workpiece 100 which was moved along rails 102. In this wire bonding position heat block 104 has been raised to meet the lower surface of workpiece 100. Device clamp 106 has been lowered to secure workpiece 100 against heat block 104. In this closed position (i.e., with heat block 104 in the raised position and device clamp 106 in the lowered position) wire loops 100a are formed in a wire bonding operation.
After a wire bonding operation is complete (or a portion of the wire bonding operation is complete) the workpiece is moved. For example, the wire bonding of the entire workpiece may be complete and the workpiece is to be moved to a post bonding location. Alternatively, the wire bonding of a portion of the workpiece may be complete, but another portion of the workpiece still needs to be wire bonded. In order to wire bond the other portion of the workpiece, the workpiece is moved.
In either of these two cases, in order to move the workpiece (e.g., along the rails) the device clamp is raised to an open location and the heat block is lowered to an open position. Referring now to FIG. 1B, device clamp 106 has been raised to the open position and heat block 104 has been lowered to the open position. These open positions are predetermined to allow sufficient clearance for the workpiece (including the wire loops bonded to the workpiece) to be moved along the rails.
Unfortunately, when device clamp 106 and heat block 104 are moved to the predetermined open positions shown in FIG. 1B certain problems may result. For example, because of the non-uniform heat expansion of workpiece 100 (e.g., leadframe 100), workpiece 100 may buckle (where such buckling is labeled as “BUCK” in FIG. 1B) causing undesirable vibration (where such vibration is labeled as “VIB” in FIG. 1B). Further, the uncontrolled buckling of workpiece 100 may also cause contact (where such contact is labeled as “CONT” in FIG. 1B) between the wire loops 100a on workpiece 100 and device clamp 106, for example, during indexing.
Thus, it would be desirable to provide improved methods of operating clamping systems for wire bonding machines.